A. Technical Field
This invention relates generally to optical communication networking systems, and more particularly, to an array of banded semiconductor operational amplifiers integrated within a photonic integrated circuit.
B. Background of the Invention
The importance of optical networks in today's society is well understood. Many optical communication systems use wavelength division multiplexing (hereinafter, “WDM”), which multiplexes and routes wavelengths or channels between nodes within the network. WDM optical systems allow a service provider to scale a network by adding or removing wavelengths which allows scalability of bandwidth with minimal physical buildout of the network.
WDM networks can increase the total number of channels and density of these channels to improve network bandwidth. Dense wavelength division multiplexed (hereinafter, “DWDM”) systems and course wavelength division multiplexed (hereinafter, “CWDM”) systems provide a service provider with different channel characteristics that may be applied to various optical networking applications.
CWDM systems transmit fewer channels and uses wider spacing between the channels when compared to DWDM systems. As a result, CWDM systems are typically deployed in short to mid haul applications whereas DWDM systems are primarily used in long haul scenarios. The management of these optical systems and the wavelengths therein, may vary depending on the particular characteristics of the system and the environment in which it operates.
An optical add drop multiplexer (hereinafter, “OADM”) is one such device used in WDM systems for multiplexing and routing different channels of light into or out of a WDM signal. In performing an optical demultiplexing or drop operation, an OADM receives a WDM signal and separates at least one wavelength from the WDM signal. An OADM also performs an optical multiplexing or add operation by combining at least two wavelengths into a single WDM signal.
A reconfigurable OADM (hereinafter, “ROADM”) allows a service provider to dynamically configure wavelengths that are added and/or dropped. A typical ROADM comprises three stages: an optical demultiplexer, a structure that allows for reconfiguration of added and/or dropped wavelengths, and an optical multiplexer. One skilled in the art will recognize that there are a variety of manufacturing technologies used to design and construct these ROADMs. For example, technologies such as thin film filters, fiber gratings with optical circulators, free space grating devices and integrated planar arrayed waveguide gratings may be used to build ROADMs. Thin film filters are known for their high performance in lower channel count applications and planar light circuits are stronger in higher channel counts with a high degree of integration.
Optical systems require the signals within a network be maintained within a particular power range. In order for networking nodes to function properly, an optical signal should meet certain parameters such as power, signal-to-noise ratio, etc. If an optical signal fails to comply with these parameters, then errors may occur within the network.
Amplifiers within the optical system are provided to maintain optical signal power within a preferred range. Examples of such amplifiers include Erbium-doped fiber amplifiers (hereinafter, “EDFA”) and semiconductor optical amplifiers (hereinafter, “SOA”). EDFAs are commonly deployed within legacy optical networks but have bandwidth constraints that limit their applications. EDFAs typically operate from bandwidths of 1530 nm to 1620 nm and fail to provide proper amplification for wavelengths outside of this bandwidth range.
SOAs are currently being deployed within optical systems and provide improved bandwidth performance over the previously described EDFAs. For example, SOAs can achieve relatively higher bandwidths on the order of 60 to 100 nm. A typical bandwidth range addressable by SOAs is between 1240 nm to 1675 nm, which is much larger than EDFAs provide.
As the need to address bandwidths within a broader range increase, the amplification and maintenance of optical signals within WDM networks becomes more challenging.